Today dimensional measurements may be made by handheld measuring instruments that are not automated or by fixed instruments that are automated. Examples of such handheld instruments include triangulation scanners such as structured light scanners. Another example of a handheld instrument is a laser tracker having an operator that carries around a spherically mounted retroreflector (SMR) to determine 3D coordinates of points in contact with the SMR. An example of an instrument that can be automated but is fixed in place is a Cartesian CMM. Another example of an automated instrument fixed in place is a robot that holds a measurement device such as a triangulation scanner, also referred to as a 3D imager. In some cases, 3D measuring devices combine tactile measuring capability with non-contact scanning capability.
A difficulty commonly encountered in making 3D measurements of complex objects is that, in some cases, the 3D measuring instruments such as scanners are registered using an external 3D coordinate measuring device such as a laser tracker, which provides a direct registration to a global environment, while in other cases the 3D measuring instruments do not have connection to a device providing a direct registration to a global environment. There is a need today for coordinating registration of 3D data collected in these different cases. One example of such a need is in measuring an internal feature such as a hole with a tactile probe when there is no method for directly registering the tactile probe with an external 3D measuring device. Yet another opportunity is to devise measuring devices having added capability in making 3D measurements in interior and exterior regions of an object under test.
While existing 3D measuring devices such as scanners are suitable for their intended purposes, what is needed is a device having improved ability to combine globally registered and locally registered 3D measurement data.